The best replacement for air filter is air purifier.

The best alternatives to air filter are rated as following:
★★★★★  air purifier
★★★★★  cold air intake
★★★★  air intake
★★★★  cabin air filter
★★★  induction kit
★★  oil filter
★★  ionizer
★★  furnace filter
★★  dehumidifier
★  cabin filter
★  purifier
★  intake
★  fuel filter
★  no air filter
★  flame arrestor
★  microfilter
★  velocity stack
★  pod filter
  k&n
  fram air filter
  oem
  fram
  aftermarket
  k&n air filter
  air filter
  cai
  dry
  purolator air filter

Your alternative for air filter is not listed? Suggest!
Speaking about air filter, one probably shouldn't forget about fan.

Other search terms related to air filter and their ratings are:
★★★★★ fan
★★★ built in velocity stack
★ velocity stack
You have in mind a companion for air filter and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of air filter in all years. Click on graph for more.
air filter
air purifier
cold air intake